Such bottles or similar containers can be used for fluids, for example drinks. The containers can be made of a transparent or translucent material, for example glass, or a translucent plastic, e.g. PET.
It is known to inspect such containers for unwanted foreign matter in the filled product by means of an inspection device, not only for reasons of consumer health but if such foreign matter is found, it can ruin the reputation of the product manufacturer concerned. Therefore such a foreign matter inspection is performed with great care in order e.g. to prevent possible product liability claims.
Such foreign matter inspections can be carried out with optical inspection devices as disclosed e.g. in DE 102 57 238 A1 or devices based on X-ray radiation (for example DE 202 17 559 U1; DE 10 2006 048 327 A1; DE 202 18 138 U1).
These systems which function well in principle however have their limits if the containers to be inspected are very dark or even opaque, such as for example metal cans, or if the product is very cloudy and/or contains solids or fibres.
An inspection method is also known in which a piezo sensor is used under laboratory conditions as disclosed in AiF Report 264 ZBG (Novel multicontact detection as a basis for an innovative hybrid system for automatic detection of particulate solid foreign bodies in filled, flowable, non-lumpy foodstuffs on the example of products of selected rheological constitution; Delgado, Antonio; Benning, Rainer; Forstner, Judith; Erlangen; FAU Erlangen-Nürnberg, 2009 (AIF264ZBG)).
The procedure disclosed in AIF264ZBG is intended to be suitable for detecting foreign bodies in fluids by means of signal reception by the piezo sensor and vibration analysis after excitation of the fluid. The containers used for the tests performed were 0.5 liter bottles as used for beer or soft drinks. For the digital simulation by means of the finite element method (ANSYS CFX simulation software), for example a bottle filled with water was selected in order to investigate whether a translational or a rotational acceleration is most suitable for positioning. The foreign bodies were substantially spherical glass particles with diameters 0.5 mm, 1.0 mm and 1.5 mm. In addition theoretical tests were first performed with PET particles but also with olive oil. The clamping force can be set in a defined manner by the adjustability of the upper bottle centring and the sprung mounting of the base. The latter also achieves a comparatively simple implementation of the necessary decoupling from vibrations acting from the outside. The signal reception by the piezo sensor takes place exclusively via the base of the bottle in that the piezo sensor is glued directly onto the base of the bottle.
In principle in this way foreign matter can also be detected in containers and/or products which are difficult to inspect. However the findings of the report are based solely on laboratory measurements.